User:Philcha/Sandbox/Chelicerata

Lead (copied in)

The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda, and includes horseshoe crabs, scorpions, spiders, mites. They originated as marine animals, possibly in the Cambrian period, but the first confirmed chelicerate fossils, eurypterids, date from a little over 445 million years ago in the Late Ordovician period. Although only four marine species survive, all of them horseshoe crabs, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species.

Like all arthropods, chelicerates have segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins. Chelicerates' bodies consists of two tagmata, the cephalothorax and abdomen, except that mites have no visible division between these sections. The chelicerae that give the group its name are the only appendages that appear before the mouth, and in most sub-groups are modest pincers used in feeding; however spiders' chelicerae form fangs that most species use to inject venom into their prey. The group has the typical arthropod open circulatory system, in which a tube-like heart pumps blood through the hemocoel, which is the major body cavity. Marine chelicerates have gills while the air-breathing forms generally have both book lungs and tracheae. In general the ganglia of living chelicerates' central nervous systems fuse into large masses in the cephalothorax, but there are wide variations and this fusion is very limited in the Mesothelae, which are regarded as the oldest and most primitive group of spiders. Most chelicerates rely on modified bristles for information about chemical changes and about touch, vibrations and air currents. However the most active hunting spiders have very acute eyesight. Chelicerates were originally predators but the group has diversified to use all the major feeding strategies: predation, parasitism, herbivory, scavenging and eating decaying organic matter. Although harvestmen can digest solid food, the guts of most modern chelicerates are too narrow for this and they generally liquidize their food by grinding it with their chelicerae and pedipalps and flooding it with digestive enzymes. To conserve water, air-breathing chelicerates excrete waste as solids that are removed from their blood by Malphigian tubules, structures which also evolved independently in insects. While the marine horseshoe crabs rely on external fertilization, air-breathing chelicerates use internal but usually indirect fertilization. Predatory species generally use elaborate courtship rituals to prevent males from being eaten before they can mate. Most lay eggs that hatch as what look like miniature adults, but all scorpions and a few species of mites keep the eggs inside their bodies until the young emerge. In most chelicerate species the young have to fend for themselves, but in scorpions and some species of spider the females protect and feed their young.

The evolutionary origins of chelicerates from the early arthropods have been debated for decades. Although there is considerable agreement about the relationships between most chelicerate sub-groups, the position of scorpions is still controversial.

Although the venom of a few spider and scorpion species can be very dangerous to humans, medical researchers are investigating the use of these venoms for the treatment of disorders ranging from cancer to erectile dysfunction. The medical industry also uses the blood of horseshoe crabs as a test for the presence of dangeous bacteria. Genetic engineers have experimented with modifying goats' milk and plants' leaves to produce spider silk. Mites can cause allergies in humans, transmit several diseases to humans and their livestock, and are serious agrucultural pests.

Lead (v 1)

The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda, and includes horseshoe crabs, scorpions, spiders, mites. They originated as marine animals, possibly in the Cambrian period, but the first confirmed chelicerate fossils, eurypterids, date from a little over 445 million years ago in the Late Ordovician period. Although only four marine species survive, all of them horseshoe crabs, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species.

Chelicerates' segmented bodies consist of two tagmata, the cephalothorax and abdomen, except that mites have no visible division between these sections. The chelicerae that give the group its name are the only appendages that appear before the mouth, and in most sub-groups are modest pincers used in feeding; however spiders' chelicerae form fangs that most species use to inject venom into their prey. In general the ganglia of living chelicerates' central nervous systems fuse into large masses in the cephalothorax, but there are wide variations and this fusion is very limited in the Mesothelae, the oldest and most primitive group of spiders. Most chelicerates rely on the equivalents of smell and touch, but the most active hunting spiders have very acute eyesight. Chelicerates were originally predators but the group has diversified to use all the major feeding strategies: predation, parasitism, herbivory, scavenging and eating decaying organic matter. The guts of most modern chelicerates are too narrow for solid material and they generally liquidize their food before ingesting it. Air-breathing chelicerates have developed respiratory and excretory systems that minimize water loss. They also use internal fertilization, and predatory species use elaborate courtship rituals to prevent males from being eaten before they can mate. Most lay eggs that hatch as what look like miniature adults, but all scorpions and a few species of mites are ovoviparous. In most species the young have to fend for themselves, but in scorpions and some species of spider mothers protect and feed their young.

The evolutionary origins of chelicerates from the early arthropods have been debated for decades. Although there is considerable agreement about the relationships between most chelicerate sub-groups, the position of scorpions is still controversial.

Although the venom of a few spider and scorpion species can be very dangerous to humans, medical researchers are investigating the use of these venoms for the treatment of disorders ranging from cancer to erectile dysfunction. The medical industry also uses the blood of horseshoe crabs as a test for the presence of dangeous bacteria. Genetic engineers have experimented with modifying goats' milk and plants' leaves to produce spider silk. Mites can cause allergies in humans, transmit several diseases to humans and their livestock, and are serious agricultural pests.

RE

See strikethroughs and new sections below. The first paragraph seemed shaky (e.g., "there may be about 500,000 unidentified species"). And, a good taxonomy page includes ONLY defining characters, top-down--if there are many exceptions, they belong on a lower taxon's article. Some of this info is great, but this is an encyclopedia, not a whole book on the group. StevePrutz (talk) 19:42, 30 October 2008 (UTC)

(intro)

The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda, and includes horseshoe crabs, scorpions, spiders, mites. They originated as marine animals, possibly in the Cambrian period, but the first confirmed chelicerate fossils, eurypterids, date from a little over 445 million years ago in the Late Ordovician period. Although only four marine species survive, all of them horseshoe crabs, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species.

Chelicerates' segmented bodies consist of two tagmata, the cephalothorax and abdomen, except that mites have no visible division between these sections.

Etymology

The chelicerae that give the group its name are the only appendages that appear before the mouth, and in most sub-groups are modest pincers used in feeding; however spiders' chelicerae form fangs that most species use to inject venom into their prey. In general the ganglia of living chelicerates' central nervous systems fuse into large masses in the cephalothorax, but there are wide variations and this fusion is very limited in the Mesothelae, the oldest and most primitive group of spiders. Most chelicerates rely on the equivalents of smell and touch, but the most active hunting spiders have very acute eyesight.

Physical description

Chelicerates were originally predators but the group has diversified to use all the major feeding strategies: predation, parasitism, herbivory, scavenging and eating decaying organic matter. The guts of most modern chelicerates are too narrow for solid material and they generally liquidize their food before ingesting it. Air-breathing chelicerates have developed respiratory and excretory systems that minimize water loss. They also use internal fertilization, and predatory species use elaborate courtship rituals to prevent males from being eaten before they can mate. Most lay eggs that hatch as what look like miniature adults, but all scorpions and a few species of mites are ovoviparous. In most species the young have to fend for themselves, but in scorpions and some species of spider mothers protect and feed their young.

The evolutionary origins of chelicerates from the early arthropods have been debated for decades. Although there is considerable agreement about the relationships between most chelicerate sub-groups, the position of scorpions is still controversial.

Toxicity and medicine

Although the venom of a few spider and scorpion species can be very dangerous to humans, medical researchers are investigating the use of these venoms for the treatment of disorders ranging from cancer to erectile dysfunction. The medical industry also uses the blood of horseshoe crabs as a test for the presence of dangeous bacteria. Genetic engineers have experimented with modifying goats' milk and plants' leaves to produce spider silk. Mites can cause allergies in humans, transmit several diseases to humans and their livestock, and are serious agricultural pests.

Lead (v 2 - Philcha)

The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda, and includes horseshoe crabs, scorpions, spiders, mites. The first confirmed chelicerate fossils, marine eurypterids, date from a little over 445 million years ago in the Late Ordovician period. Although only four marine species survive, there are over 77,000 recognized living species of air-breathing chelicerates.

Chelicerates' segmented bodies consist of two tagmata, the cephalothorax and abdomen, except that mites have no visible division between these sections. The chelicerae that give the group its name are the only appendages that appear before the mouth, and in most sub-groups are modest pincers used in feeding; however spiders' chelicerae form fangs. In general the ganglia of living chelicerates' central nervous systems fuse into large masses in the cephalothorax, but there are wide variations between chelicerate sub-groups. Chelicerates were originally predators but the group has diversified to use all the major feeding strategies: predation, parasitism, herbivory, scavenging and eating decaying organic matter. The guts of most modern chelicerates are too narrow for solid material and they generally liquidize their food before ingesting it. Air-breathing chelicerates use internal fertilization, and predatory species use elaborate courtship rituals to prevent males from being eaten before they can mate. Most lay eggs that hatch as "miniature adults", but all scorpions and a few species of mites are ovoviparous. In most species the young have to fend for themselves, but in scorpions and some species of spider mothers protect and feed their young.

The evolutionary origins of chelicerates from the early arthropods have been debated for decades. Although there is considerable agreement about the relationships between most chelicerate sub-groups, the position of scorpions is still controversial.

Although the venom of a few spider and scorpion species can be very dangerous to humans, medical researchers are investigating the use of these venoms for the treatment of disorders ranging from cancer to erectile dysfunction. The medical industry also uses the blood of horseshoe crabs as a test for the presence of dangeous bacteria. Genetic engineers have experimented with modifying goats' milk and plants' leaves to produce spider silk. Mites can cause allergies in humans, transmit several diseases to humans and their livestock, and are serious agricultural pests.

Lead (v 2 - StevePrutz)

The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda, and includes horseshoe crabs, scorpions, spiders, mites. The first confirmed chelicerate fossils, marine eurypterids, date from a little over 445 million years ago in the Late Ordovician period. Although only four marine species survive, there are over 77,000 recognized living species of air-breathing chelicerates.

Paragraph 1: I am confused about the "marine vs. air-breathing" last sentence. Do the marine chelicerates respire underwater, and are the 77,000 others strictly non-marine animals?

Chelicerates' segmented bodies consist of two tagmata, the cephalothorax and abdomen, except that mites have no visible division between these sections. The chelicerae that give the group its name are the only appendages that appear before the mouth, and in most sub-groups are modest pincers used in feeding; however spiders' chelicerae form fangs. In general the ganglia of living chelicerates' central nervous systems fuse into large masses in the cephalothorax, but there are wide variations between chelicerate sub-groups. Chelicerates were originally predators but the group has diversified to use all the major feeding strategies, including: predation, parasitism, herbivory, scavenging and eating decaying organic matter. The guts of most modern chelicerates are too narrow for solid material and they generally liquidize their food before ingesting it. Air-breathing (???) chelicerates use internal fertilization, and predatory species use elaborate courtship rituals to prevent males from being eaten before they can mate (huh? courtship rituals prevent the winners from being eaten?). Most lay eggs that hatch as "miniature adults", but all scorpions and a few species of mites are ovoviparous. In most species the young have to fend for themselves, but in scorpions and some species of spider mothers care for protect and feed their young.

Paragraph 2: see bold and strikethrough edits above.

The evolutionary origins of chelicerates from the early arthropods have been debated for decades. Although there is considerable agreement about the relationships between most chelicerate sub-groups, the position of scorpions is still controversial.

Paragraph 3: looks OK.

Although the venom of a few spider and scorpion species can be very dangerous to humans, medical researchers are investigating the use of these venoms toxins for the treatment of disorders ranging from cancer to erectile dysfunction. The medical industry also uses the blood of horseshoe crabs as a test for the presence of dangerous harmful bacteria. Genetic engineers have experimented with modifying goat milk and plant leaves to produce spider silk. Mites can cause allergies in humans, transmit several diseases to humans and their livestock, and are serious agricultural pests.

Paragraph 4: some of this is more relevant on the mite and spider main articles. StevePrutz (talk) 00:22, 31 October 2008 (UTC)